Small molecule mediated biosensing using carbon nanotubes in homogeneous format

Abstract

Nanosensors for detecting target analytes and methods of detecting analytes have been developed in which a small molecule effector concentration is altered thereby causing changes in carbon nanotube conductance. The nanosensor operates in a homogeneous format, not requiring the immobilization of the target analyte for detection.

1 . A nanosensor for detecting the presence of an analyte comprising: 
 a) at least two electrodes connected by an electrically conducting path comprised of one or more carbon nanotubes wherein at least one of said carbon nanotubes is semiconducting, and wherein the carbon nanotube is in contact with an effector; and    b) at least one reporter molecule having an analyte as a reporter substrate.    
   
   
       2 . A nanosensor for detecting the presence of a catalytic analyte comprising: 
 a) at least two electrodes connected by an electrically conducting path comprised of one or more carbon nanotubes wherein at least one of said carbon nanotubes is semiconducting, and wherein the carbon nanotube is in contact with an effector; and    b) a reporter substrate that is a substrate of an catalytic analyte.    
   
   
       3 . A nanosensor for detecting the presence of an analyte comprising: 
 a) at least two electrodes connected by an electrically conducting path comprised of one or more carbon nanotubes wherein at least one of said carbon nanotubes is semiconducting, wherein the carbon nanotube is in contact with an effector; and    b) an effector responsive to the presence of an analyte.    
   
   
       4 . A nanosensor for detecting the presence of an analyte comprising: 
 a) at least two electrodes connected by an electrically conducting path comprised of one or more carbon nanotubes wherein at least one of said carbon nanotubes is semiconducting, wherein the carbon nanotube is in contact with an effector;    b) a reporter molecule comprising an activity switch comprising an analyte receptor linked to a reporter inhibitor; and    c) a reporter substrate that is a substrate of the reporter molecule.    
   
   
       5 . A nanosensor according to any of claims  1 ,  2 ,  3 , or  4  optionally comprising a gate electrode.  
   
   
       6 . A nanosensor according to any of claims  1 ,  2 ,  3 , or  4  wherein the carbon nanotube is suspended between at least two electrodes.  
   
   
       7 . A nanosensor according to any of claims  1 ,  2 ,  3 , or  4  wherein the carbon nanotube is supported on a support.  
   
   
       8 . A nanosensor according to  claim 7  wherein the support is comprised of materials selected from the group consisting of silicon, polysilicon, silicon dioxide, silicon nitride, polymeric materials, glass, agarose, nitrocellulose, nylon, insulating materials.  
   
   
       9 . A nanosensor according to  claim 1  or  4  wherein the reporter molecule is an enzyme.  
   
   
       10 . A nanosensor according to  claim 2  wherein the analyte is an enzyme.  
   
   
       11 . A nanosensor according to either of claims  9  or  10  wherein the enzyme is selected from the group consisting of glucose oxidase, laccase, ascorbate oxidase, bilirubin oxidase, glutaminase, alphahydroxy acid oxidase, aldehyde oxidase, L-amino acid oxidase, ascorbate oxidase, cholesterol oxidase, and xanthine oxidase and asparaginase.  
   
   
       12 . A nanosensor according to any of claims  1 ,  2 ,  3 , or  4  wherein the effector is selected from the group consisting of oxygen, ammonia, nitrogen dioxide, and hydrogen ions.  
   
   
       13 . A nanosensor according to  claim 2  or  4  wherein the reporter substrate is selected from the group consisting of glucose, bilirubin, ascorbate, glutamine, and asparagine.  
   
   
       14 . A nanosensor according to any of claims  1 ,  2 ,  3 , or  4  wherein the carbon nanotube is substantially free of metal.  
   
   
       15 . A method for detecting an analyte comprising: 
 a) providing a nanosensor comprising: 
 i) at least two electrodes connected by an electrically conducting path comprised of one or more carbon nanotubes wherein at least one of said carbon nanotubes is semiconducting, and wherein the carbon nanotube is in contact with an effector and has a baseline conductance; and  
 ii) a reporter molecule having an analyte as a substrate;  
   b) providing a sample suspected of containing an analyte;    c) contacting the sample of (b) with the reporter molecule of (a) wherein the concentration of the effector molecule is altered resulting in a change in the conductance of the carbon nanotube with respect to the baseline conductance; and    d) measuring the change in conductance of the carbon nanotube with respect to the baseline conductance whereby the presence of the analyte is detected.    
   
   
       16 . A method for detecting a catalytic analyte comprising: 
 a) providing a nanosensor comprising: 
 i) at least two electrodes connected by an electrically conducting path comprised of one or more carbon nanotubes wherein at least one of said carbon nanotubes is semiconducting, and wherein the carbon nanotube is in contact with an effector and has a baseline conductance; and  
 ii) a reporter substrate that is a substrate of a catalytic analyte;  
   b) providing a sample suspected of containing a catalytic analyte;    c) contacting the sample of (b) with the reporter substrate of (a) wherein the concentration of the effector molecule is altered resulting in a change in the conductance of the carbon nanotube with respect to the baseline conductance; and    d) measuring the change in conductance of the carbon nanotube with respect to the baseline conductance whereby the presence of the catalytic analyte is detected.    
   
   
       17 . A method for detecting an analyte comprising: 
 a) providing a nanosensor comprising: 
 i) at least two electrodes connected by an electrically conducting path comprised of one or more carbon nanotubes wherein at least one of said carbon nanotubes is semiconducting, and wherein the carbon nanotube is in contact with an effector and has a baseline conductance; and  
 ii) an effector responsive to the presence of an analyte;  
   b) providing a sample suspected of containing an analyte;    c) contacting the sample of (b) with the effector of (a) wherein the concentration of the effector molecule is altered resulting in a change in the conductance of the carbon nanotube with respect to the baseline conductance; and    d) measuring the change in conductance of the carbon nanotube with respect to the baseline conductance whereby the presence of the analyte is detected.    
   
   
       18 . A method for detecting an analyte comprising: 
 a) providing a nanosensor comprising: 
 i) at least two electrodes connected by an electrically conducting path comprised of one or more carbon nanotubes wherein at least one of said carbon nanotubes is semiconducting, and wherein the carbon nanotube is in contact with an effector and has a baseline conductance; and  
 ii) a reporter molecule having an activity switch comprising an analyte receptor linked to a reporter inhibitor;  
   b) providing a sample suspected of containing an analyte which binds to the analyte receptor of the activity switch wherein the reporter molecule becomes active;    c) contacting the sample of (b) with the reporter molecule of (a) wherein the concentration of the effector molecule is altered resulting in a change in the conductance of the carbon nanotube with respect to the baseline conductance; and    d) measuring the change in conductance of the carbon nanotube with respect to the baseline conductance whereby the presence of the analyte is detected.    
   
   
       19 . A method according to any of claims  15 ,  16 ,  17 , or  18  wherein the carbon nanotube is substantially free of metal.  
   
   
       20 . A method according to any of claims  15 ,  16 ,  17 , or  18  wherein the carbon nanotube is optionally supported on a surface.  
   
   
       21 . A method according to  claim 20  wherein the surface is comprised of materials selected from the group consisting of silicon, polysilicon, silicon dioxide, silicon nitride, polymeric materials, glass, agarose, nitrocellulose, nylon, insulating materials.  
   
   
       22 . A method according to  claim 15  or  18  wherein the reporter molecule is an enzyme.  
   
   
       23 . A method according to  claim 16  wherein the analyte is an enzyme.  
   
   
       24 . A method according to either of claims  22  or  23  wherein the enzyme is selected from the group consisting of glucose oxidase, laccase, ascorbate oxidase, bilirubin oxidase, glutaminase, alphahydroxy acid oxidase, aldehyde oxidase, L-amino acid oxidase, ascorbate oxidase, cholesterol oxidase, and xanthine oxidase and asparaginase.  
   
   
       25 . A method according to  claim 16  or  17  or wherein the reporter substrate is selected from the group consisting of glucose, bilirubin, ascorbate, glutamine, and asparagine.